Protein fingerprinting is traditionally an analytical technique for protein identification in which an unknown protein of interest is cleaved into smaller peptides, the absolute masses of which are measured using a mass spectrometer such as MALDI-TOF or ESI-TOF (Clauser K R et al. Anal. Chem. 1999; 71(14): 2871-82). This traditional method requires high purity and high abundance of the proteins of interest.